Rates of Decoloration

Pseudomonas luteola Reactive azo dyes, Direct azo dyes and leather dyes The 59-99% color removal after 2-6 days static incubation, at dye concentration of 100 mg L 1, monoazo dyes showing fastest rate of decoloration [78]... 

Both purified laccase as well as the crude enzyme from the WRF Cerrena unicolor were used to convert the dyes in aqueous solution. Biotransformation of the dyes was followed spectrophotometrically and confirmed by high performance liquid chromatography. The results indicate that the decolorization mechanism follows MichaeliseMenten kinetic and that the initial rate of decolorization depends both on the structure of the dye and on the concentration of the dye. Surprisingly, one recalcitrant azo dye (AR 27) was decolorized merely by purified laccase in the absence of any redox mediator [46],... 

Two bacterial Shewanella species, S. putrefaciens and S. oneidensis, previously selected on the basis of their ability to degrade azo dyes, were also tested in saline medium at different salt concentrations of up to 10% to evaluate their potential to decolorize four structurally different azo dyes Reactive Black 5, Direct Red 81, Acid Red 88, and Disperse Orange 3. Full decolorization was reached at salt concentrations up to 6% the decolorization velocity was inversely related to salt concentration. The rate of decolorization was increased by yeast extract and a calcium source, while was decreased by glucose and by a nitrogen source [54]. 

The dependence of the rate of decoloration on temperature, espedally around the ass temperature, will be considered in Sect. 

Such rate of decoloration was initially interpreted as being the sum of two or three exponential rate proc ses, each char terized by its own rate constant (kj > k2 > ks), which should correspond to a different merocyanine isomer (Kg. 2). 

Figure 8 shows the optical density of a film (65 microm. thickness) after an irradiation period of five seconds. As can be seen, a sharp increase of photores-ponse occurs in the direct neighbourhood of Tg. On following the rate of decoloration at several temperatures an Arrhenius plot gives a sigmoid curve (Fig. 9) above 70 C the activation energy is equal to... 

Time—In theory, adsorption should be practically instantaneous however, in practice, this is not the case. The rate of decoloration is very rapid during the first few minutes after the adsorbent comes in contact with the oil and then decreases to a point where equilibrium is reached and no more color is adsorbed. Usually 15 to 20 minutes contact time is adequate at a bleaching temperature above the boiling point of water. Contact time is made up of two time periods (1) the time in the bleaching vessel and (2) the time in the filter during recirculation or final filtering. 

It is -interesting to observe here that less clear-cut separation in slow and fast isomers can occur in the kinetic scheme of the decoloration process. If the rate of decoloration depends to a considerable degree on the viscosity of the polymer matrix, it is also a very well known fact that the distribution of free volume in the glassy state can be Inhomogeneous, giving rise to a broad spectrum of relaxation times. This leads to a more complex mechanism of one-step chemical reactions in glassy polymers (111-114). 

B. The reagent contains a mixture of SchenLabs (SchenLabs Pharmaceuticals Inc., New York) purified Bacillus cereus penicillinase (10,000 units/ml), 1% starch, 0.1 iV iodine and M sodium phosphate buffer, pH 7, in the ratio 5 50 1 1. The rate of decolorization of the spray by the penicillin substrate is found to be dependent on the penicillinase cone, and, with this mixture, development is complete at room temperature (ca. 22°) in 10-15 min after hydrolysis of the j8-lactam ring with alkali or penicillinase. The resulting penicilloic acid rapidly consumes nine equivalents of iodine. Under suitable conditions it is found that both penicillins and the related products cepha-... 

The O3/H2O2/UV is suitable for the treatment of dye in textile industry effluents, because the H2O2/UV process shows a slower rate of decolorization than ozonation, which is more effective in TOC removal. The combination of the two methods allows both a high rate of decolorization and TOC removal. 

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